The invention relates to an individual wheel suspension for vehicles, especially for vehicles built on a traditional heavy vehicle frame using longitudinal beams.
Individual front wheel suspensions currently used in vehicles built on a frame, such as two longitudinal U- or I-profile beams, are often of the McPherson or double wishbone type. Such solutions have been difficult to implement without severely intruding into the available space for the engine compartment. The alternative has often been to relocate the engine, as seen in e.g. buses. Examples of known types of individual front wheel suspensions are shown in DE-A1-2918605, DE-A1-4021096, DE-A1-4412145, DE-A1-19515565 and U.S. Pat. No. 4,033,605.
A further problem with currently used wheel suspensions is that they limit the possible ground clearance and the choice of engine placement. It is desirable to be able to regulate the height of the vehicle chassis above ground level, while at the same time placing the engine as low as possible, in order to achieve a low centre of gravity and a level floor in the drivers cab. As a rule it is not possible to combine these requirements with the currently used wheel suspensions, in which a sprung, rigid wheel axle extends transversely underneath the frame and the engine.
The problems that accompany the currently used wheel suspensions have been solved by using an individual wheel suspension of the type described in the claims below. According to the invention the solution involves using an individual wheel suspension for vehicles built on a longitudinal frame and comprises a steering knuckle attachment, which at its lower, outer end is connected to and journalled in a wheel spindle. Also included is a pair of upper and lower torsion rod placed in the longitudinal direction of the vehicle and journalled in the steering knuckle attachment and a transverse section of the frame, to form a parallelogram. A transverse stabilizer bar is connected to the ends of one pair of the above corresponding torsion rod, which ends are facing away from the steering knuckle attachment and positioned on either side of the vehicle. The arrangement is also provided with a first shock absorber, placed between the lower end of the steering spindle attachment and the vehicle frame, as well as an adjustable suspension device, which connects the lower end of the steering spindle attachment and the vehicle frame. The steering spindle attachment is also pivotally attached to the vehicle frame at its upper end, via an upper supporting arm, and at its lower end, via a lower supporting arm.
The vehicle frame can also be provided with a substantially rectangular frame section, comprising two mainly vertical sections, attached directly to and on either side of the vehicle frame, and two mainly horizontal sections, which connect the upper and lower ends of the vertical sections. This subframe is used for attaching the supporting arms, shock absorbers and torsion rod that carries the steering knuckle attachment.
The result is a very compact wheel suspension that does not intrude into the available space for the engine compartment, as it lacks a sprung, rigid front axle. This allows the engine to be lowered, resulting in a lower centre of gravity and allows a planar floor in the driver""s  cab without having to raise the cab higher above ground level.
As the adjustable suspension device comprises one or more bellows attached between the lower part of the steering knuckle attachment and the vehicle frame, the level of the chassis can be adjusted over a large range. The bellows are preferably arranged in pairs on either side of the supporting arms.
By using supporting arms and torsion rod in all directions, the arrangement makes it possible to control camber and changes in the track width through the entire suspension range and under varying loads. It is particularly advantageous to use longitudinal torsion rod for taking up large loads during braking, since this gives a lower bending moment on the vehicle frame, compared to the traditional angled linkages normally used for individual suspensions.